Introduction

This is a brief tutorial to make the Brother MFC-420CN printer/scanner work on Arch. While this tutorial is based on the MFC-420CN specifically, it can be used as a general guide for most Brother MFC model printers (substituting MFC-420CN for your model where needed).
On Brother's Linux Driver page you can find extra information along with drivers for different printer models.

Printer

Prerequisites

This tutorial assumes you have the following packages installed. Failure to do so may result in hard to trace issues with printing.

Download printer drivers

Brother actively supplies Linux drivers for it's MFC series printers in RPM and DEB formats. Luckily there are tools to change these formats into something Arch can use.

First create a temporary directory.

Then you must download the official LPR drivers from the Brother website into this directory. Click here to download the MFC-420CN LPR driver (RPM archive).

You should also download the CUPS wrapper script. Click here to download the MFC-420CN CUPS wrapper script (RPM archive). This script creates the filters and PPD file for CUPS automatically saving us from extra work.

Extracting the RPM files

Now you need a small script called rpmextract which allows you to extract files from the RPM you've just downloaded.

Editing files to make it work with Arch

Arch Linux uses its own file system organization, so we'll have to edit some files. Assuming you are still in the temporary directory you created. You can use your favorite text editor to edit usr/local/Brother/cupswrapper/cupswrapperMFC420CN-1.0.0 and change all instances of /etc/init.d/ to /etc/rc.d/OR you can just do the following.

Once you've finished this step, copy all of the files to their corresponding directories in your file system :

# cp -r usr/* /usr

Installing the printer (Local USB)

The kernel module usblp must be blacklisted before installing the driver, otherwise the Device URI will be wrong and the printer won't work.

To disable the module, edit /etc/rc.conf as shown:

/etc/rc.conf

MODULES=(... !usblp ...)

Warning: Blacklisting modules in rc.conf has been obsoleted and no longer works in initscripts 2011.06.1-1, so you'll have to use the following method.

Create a .conf file inside /etc/modprobe.d/ and blacklist the module as follows:

/etc/modprobe.d/blacklist.conf

# Do not load the usblp module on boot
blacklist usblp

Note: The blacklist command will blacklist a module so that it will not be loaded automatically, but may be loaded if another non-blacklisted module depends on it, or if it is loaded manually.

However, there is a workaround for this behaviour; the install command instructs modprobe to run a custom command instead of inserting the module in the kernel as normal, so you can force the module to always fail loading with:

/etc/modprobe.d/blacklist.conf

...
install usblp /bin/false
...

This will effectively "blacklist" that module and any other that depends on it.

Reboot the box to take effect, or manually remove the module without rebooting:

# modprobe -r usblp

Now lets plug in the printer and run the script to install the driver for us.

As root in terminal:

/usr/local/Brother/cupswrapper/cupswrapperMFC420CN-1.0.0

It will stop the cups daemon if it's running, and restart it.

Warning: Daemon may fail to start due to bug in csh. If "Unknown colorls variable `mh'." message is displayed, before starting daemon, execute:

unset LS_COLORS

Now go to the CUPS setup page: http://localhost:631/
Click on Manage Printers you should see your MFC-420CN printer automatically installed and configured. Print a test page!

If the test page fails with error "Printer not connected; will retry in 30 seconds..." then.

Click Delete Printer and remove the automatically created printer.

Click Administration --> Find New Printers

You should see your Brother printer listed here, add it!

Print a test page

NOTE: Be sure to add cupsd to the DAEMON line in rc.conf so it loads everytime at startup.

Installing the printer (Network, Ethernet)

Now lets run the script to install the driver for us.

As root in terminal:

/usr/local/Brother/cupswrapper/cupswrapperMFC420CN-1.0.0

It will stop the cups daemon if it's running, and restart it.

Warning: Daemon may fail to start due to bug in csh. If "Unknown colorls variable `mh'." message is displayed, before starting daemon, execute:

Now copy the files to their corresponding directories in your file system:

# cp -r /path/to/brscan/usr/* /usr

Now you'll need to add "brother2" to the end of /etc/sane.d/dll.conf
Brother felt it necessary to include a script to do that, so you can also run:

# /usr/local/Brother/sane/setupSaneScan2 -i

For a networked brother scanner:

# brsaneconfig2 -a name=[ANY_NAME] model=[EXACT_MODEL] ip=[IP_ADDR]

Example:

# brsaneconfig2 -a name=MFC420CN model=MFC-420CN ip=10.1.1.90

To test the networked scanner, you can install xsane:

# pacman -S xsane

And run it to verify the installation (as a luser):

$ xsane

Scan Key Install (Optional)

This allows the scanner to be recognized in other programs such as GIMP. This information is a condensed and consolidated version off of Brother's linux support site (Link)

You'll need to extract the files to a temp path:

$ rpmextract.sh brscan-skey-0.2.1-1.i386.rpm

While in the directory that contains the extracted content, run:

# cp -r ./usr/* /usr

Run the setup script for brscan-key:

# /usr/local/Brother/sane/brscan-skey-0.2.1-1.sh

Execute the tool to verify that the previously installed scanner is recognized:

# brscan-skey -l

Expect the following output:

# brscan-skey -l
MFC420CN : brother2:net1;dev0 : 10.1.1.90 Active

After you receive the above output via brscan-key, check the File-> Create list in GIMP (tested v. 2.6.4) and there should be two more entries:

XSane: Device Dialog...
XSane: brother2:net1;dev0

If the new entries appear, congratulations! Your (networked) Brother scanner is now available via any XSane interface!

Troubleshooting

I can scan as root, but not as a normal user

Make sure your user is in the scanner group:

# gpasswd -a username scanner

then log out and back in.

If you still can't scan as a normal user, check that /usr/lib/sane (or /usr/lib64/sane for 64 bit) are readable and executable for your user/group.

64 bit caveat

(Note: recent Arch update merged lib64 into lib, so this may not be needed any more; you may still need to move the files back into /usr/lib, instead of /usr/lib64)

The 64 bit RPM has two files in /usr/lib64/, along with two symlinks to each file. However, the Arch64 Sane package will probably look in /usr/lib/ rather than /usr/lib64/, so we'll need to create some more symlinks. And since the symlinks reference the absolute path, not the relative path, ie: